Ozone Standard Exceedances in National Parks
The National Park Service (NPS) actively monitors ozone at its parks from April to October. Ozone measurements are compared with the National Ambient Air Quality Standard (NAAQS) for ozone. The Environmental Protection Agency (EPA) sets this standard as the level at which the ozone in the air becomes unhealthy. The NPS tracks the days when the standard is exceeded in the parks.
This past spring, EPA made the ozone standard more stringent (lowering it from 85 parts per billion (ppb) to 75 ppb). As a result, many more parks have been added to the list of exceedances. The table below displays the parks and the ozone values along with the number of days when the daily maximum 8-hour average ozone concentration equaled or exceeded 76ppb†. The fourth highest ozone column has been color-coded for easier viewing.
The thumbnails on the left access detailed ozone information maps, both season to date and current.
2009 Ozone Standard Exceedances
| April | May | June | July | Aug. | Sept. | Oct. | 2009 Season | |||
|---|---|---|---|---|---|---|---|---|---|---|
| Validation Level * | 2 | 2 | 2 | 2 | 2 | 0 | Total Count | Max 8-hr O3 (ppb) |
4th highest max. 8-hr O3 (ppb) |
|
| National Park | Count | Count | Count | Count | Count | Count | Count | |||
| Acadia– McFarland Hill | 0 | 1 | 0 | 0 | 0 | 0 | – | 1 | 86 | 73 |
| Acadia– Cadillac Mountain | 0 | 0 | 0 | 0 | 1 | 0 | – | 1 | 77 | 61 |
| Cape Cod– State Site | 0 | 0 | 0 | 0 | 2 | 0 | – | 2 | 82 | 72 |
| Death Valley– Park Village | 0 | 0 | 0 | 0 | 2 | 0 | – | 2 | 86 | 70 |
| Great Smoky Mountains– Cade's Cove | 0 | 0 | 0 | 0 | 0 | 0 | – | 0 | 67 | 62 |
| Great Smoky Mountains– Clingman's Dome | 0 | 0 | 0 | 0 | 0 | 0 | – | 0 | 72 | 71 |
| Great Smoky Mountains– Cove Mountain | 0 | 0 | 0 | 0 | 0 | 0 | – | 0 | 74 | 70 |
| Great Smoky Mountains– Look Rock | 0 | 0 | 1 | 0 | 0 | 0 | – | 1 | 84 | 69 |
| Joshua Tree– Black Rock | 3 | 10 | 10 | 15 | 18 | 3 | – | 59 | 104 | 93 |
| Joshua Tree– Cottonwood Canyon | 1 | 4 | 2 | 3 | 1 | 0 | – | 11 | 85 | 81 |
| Joshua Tree– Pinto Wells | 2 | 1 | 0 | 0 | 1 | 0 | – | 4 | 82 | 78 |
| Mammoth Cave– Houchin Meadow | 0 | 0 | 0 | 0 | 0 | 0 | – | 0 | 69 | 65 |
| Mojave– Kelso Mountains | 1 | 0 | 1 | 2 | 7 | 2 | – | 13 | 85 | 80 |
| Pinnacles– SW of East Entrance Stn. | 0 | 0 | 0 | 0 | 0 | 0 | – | 0 | 73 | 71 |
| Rocky Mountain– Long's Peak | 0 | 0 | 0 | 0 | 0 | 0 | – | 0 | 75 | 68 |
| Sequoia and Kings Canyon– Ash Mountain | 0 | 4 | 9 | 26 | 15 | 16 | – | 70 | 100 | 98 |
| Sequoia and Kings Canyon– Lower Kaweah | 0 | 0 | 0 | 12 | 5 | 1 | – | 18 | 85 | 80 |
| Yellowstone– Water Tank | 0 | 0 | 0 | 0 | 0 | 1 | – | 1 | 93 | 63 |
| Yosemite– Glacier Point | 0 | 0 | 0 | 0 | 0 | 1 | – | 1 | 76 | 72 |
| Yosemite– Turtleback Dome | 1 | 0 | 0 | 0 | 6 | 2 | – | 9 | 86 | 79 |
| Zion National Park– Dalton's Wash | 1 | 0 | 0 | 0 | 0 | 0 | – | 1 | 78 | 68 |
 *Validation level 0 indicates raw data. Validation level 1 indicates preliminary data. Validation
level 2 indicates final, validated data.Counts of days with 8-hr average ozone greater than 75 ppb may change after the data is fully validated. The ozone season runs from April to October for the detailed current ozone conditions. During the winter, more limited numbers of locations and web products are available. †The current NAAQS is 0.075 parts per million (ppm), daily maximum 8–hour average. The ozone standard is violated at an ambient air quality monitoring site when the 3-year average of the annual fourth–highest daily maximum 8–hour average ozone concentration is greater than 0.075 ppm, which occurs when the 3–year average exceeds 0.075 ppm (75 parts per billion or ppb). An exceedance occurs when the daily maximum 8–hour average is greater than 0.075 ppm (75 ppb). |
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Additional Summary Tables
(Click chart for larger image)
- Ozone 3 year Rolling 4th highest daily max 8hr average (2006)
- Ozone 1hr Days with > 125 ppb (2006)
- Detailed Summaries of 3 Year Averages of Annual 4th High Daily Max 8-hr Ozone Concentrations by park unit (2005)
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